The suspected leader of the hacker group known as Lulz Security has pleaded guilty in a U.S. court to carrying out attacks against websites of financial transaction companies such as PayPal and MasterCard.

Court papers showed that a New York court has charged 28-year-old Hector Xavier Monsegur, known as "Sabu," with 12 counts of conspiracy to engage in hacking and other crimes.

The suspect has reportedly been cooperating with the government.

Lulz Security, or LulzSec, is a spin-off of the hacking collective Anonymous.

Both have taken credit for high-profile attacks against companies and institutions including the CIA and Stratfor.

An indictment against five other members of LulzSec was due to be unsealed on March 6.
Irish police say one of the five had been arrested in Dublin.